This research work has as its objective the further clinical and pathological study of cerebral strokes due to thrombosis and hemorrhage. Stroke cases are studied clinically, arteriographically and, when circumstances allow, pathologically. The goal is to improve bedside diagnosis, identify the mechanism of the stroke and eventually devise better management and prevention. There is no experimental design to the study, only the clinicopathologic method. Bibliographic references: Duncan, G.W., Parker, S.W. and Fisher, C.M.: Acute cerebellar infarction in the PICA territory. Arch. Neurol. 32:364-368, 1975. Hochberg, F.H., Bean, C.S., Fisher, C.M. and Roberson, G.H.: Stroke in a 15-year old girl secondary to terminal carotid dissection. Neurology 725-729, 1975.